VOID FREE SOLDERING TECHNOLOGY FOR POWER ELECTRONICSAuthors: Mathias Nowottnick, Uwe Pape, and Rolf Diehm
Company: University of Rostock, Fraunhofer IZM, and Seho Systems GmbH
Date Published: 10/11/2007 Conference: SMTA International
The amount of voids can be influenced by different measures, e.g. a good wettability of metallization, solder pastes with special adopted solvents and an adequate preheating profile. However a special vacuum process step during soldering is demanded for absolutely void free solder joints. But this vacuum process is associated with some essential disadvantages. Besides of the technical expenses for vacuum pumps and additional locks, the vacuum process excludes the use of gas convection for heating and cooling. Apart from a special vapor phase – vacuum technology, most machines are using infrared radiation or heat conduction for soldering.
The same principles like vacuum soldering technology are applicable also for a higher pressure level. If the void in the solder joint is arising for an excess pressure, the normal atmosphere pressure could be sufficient for escaping of enclosed gas. Essential for this effect is the pressure difference between inside and outside of solder joint. A benefit of soldering with excess pressure is the possibility of gas convection for heat transfer. This allows the application of conventional components and the realization of the usual temperature distribution and profiles.
Key words: voids, soldering, solder paste, vacuum, pressure
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